Solder-bearing wafer for use in soldering operations

ABSTRACT

A solder-bearing wafer is provided for use in a soldering operation. The solder-bearing wafer is designed to provide a solder material which is used in a soldering operation for electrically connecting a first electronic device to a second electronic device. According to a first embodiment, the wafer comprises a substrate body having a first surface and an opposing second surface. The first surface has at least one groove formed therein and the wafer also includes at least one length of solder material securely disposed within the at least one groove. Upon heating of the at least length of solder material and placement of the substrate body between the first and second electronic devices, at least one first contact of the first electronic device is securely and electrically connected to at least one second contact of the second electronic device. The first and second electronic devices may be of a through hole type, surface mount type, or ball grid array type.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is continuation of U.S. patent application Ser. No.10/019,507, filed Mar. 29, 2002, which is a U.S. national phaseapplication under 35 U.S.C. §371 based upon co-pending InternationalApplication NO. PCT/US00/26160 filed Sep. 20, 2000, which claims thebenefit of priority of U.S. Provisional Application Ser. No. 60/154,771filed Sep. 20, 1999. The entire disclosures of the prior applicationsare incorporated herein by reference. The international application waspublished in the English language on Mar. 29, 2001 under Publication No.W001/22785.

FIELD OF THE INVENTION

The present invention relates to the field of devices for joiningconnectors or other electrical components to one another and, moreparticularly, to a method and apparatus for facilitating the solderingof first electronic devices, such as connectors, to second electronicdevices, such as printed circuit boards.

BACKGROUND OF THE INVENTION

It is often necessary and desirable to electrically connect onecomponent to another component. For example, a multi-terminal component,such as a connector, is often electrically connected to a substrate,such as a printed circuit board, so that the terminals of the componentare securely attached to contact pads formed on the substrate to providean electrical connection therebetween. One preferred technique forsecurely attaching the component terminals to the contact pads is to usea solder material around a particular area, such as a hole, whichtypically receives one component terminal. Often, the componentterminals may be in the form of conductive pins which are receivedwithin the holes formed in the substrate. The solder material, e.g.,solder paste, is generally applied around each contact hole and thenheated after the conductive pin is received within and extends throughthe contact hole. The heating of the solder paste causes the solderpaste to flow around the conductive pin and the contact hole. Thecooling of the solder paste results in the conductive pin being securelyattached to one of the contact pads formed on the substrate.

While the use of solder paste is effective in some applications, thereare a number of applications in which the use of solder paste is notdesirable due to a number of factors, including but not limited to thedesign of both the component terminals and the substrate itself. Inaddition, the use of solder paste generally does not provide asufficient volume of solder to properly join the component terminals andthe contact pads.

One alternative approach to the use of solder paste is described in U.S.Pat. No. 5,875,546, which is assigned to the assignee hereof and whichis incorporated by reference in its entirety. The device set forth inthis reference comprises an array of solder-holding clips which isreadily applied manually or by automation to a corresponding array ofconnector or other component terminals. The clips are typically formedby a die stamping operation which results in an increase in cost andcomplexity of the overall soldering operation.

It is therefore desirable to provide an alternative device and methodfor applying solder to connectors or the like.

SUMMARY OF THE INVENTION

According to a first embodiment, a solder-bearing wafer is provided foruse in a soldering operation. The solder-bearing wafer is designed toprovide a solder material which is used in a soldering operation forelectrically connecting a first electronic device to a second electronicdevice. The solder-bearing wafer may be formed of a number of materialsand preferably, the solder-bearing wafer is formed of a non-conductivematerial. For example, the solder-bearing wafer may be formed of athermoplastic, a thermoset plastic, etc. The solder-bearing wafer has aplurality of through holes formed therethrough to facilitate thesoldering of electrical terminals or contacts of the first electronicdevice. In one exemplary embodiment, the electrical terminals orcontacts comprise pins which extend outwardly from the first component.Preferably, the first electronic device comprises an electronicconnector and the second electronic device comprises a printed circuitboard.

Typically, the contacts of the first electronic device compriseconductive pins. The pins of the first electronic device are usuallyarranged in some type of pattern across the surface of the firstelectronic device. For example, a traditional first electronic devicemay have a number of rows and columns of pins which are designed toprovide a method of electrically connecting terminals of the firstelectronic device to electrical contacts disposed within the secondelectronic device, e.g., a printed circuit board. Accordingly, the waferincludes pin holes whose location and spacing correspond to the locationand spacing of the pins of the first electronic device. This permits thewafer to mate with the first electronic device such that the pins arereceived within and extend through the pin holes of the wafer. The waferis thus disposed between the first and second electronic devices.

According to the present invention, the wafer also includes a pluralityof through holes formed therethrough. The through holes are formed inrows on either side of each pin hole. The wafer further includes groovesrunning parallel to, and above and below, each row of pin holes. Thelength of each of the grooves is intersected at evenly spaced intervalsby the through holes. Preferably and according to this one exemplaryembodiment, the grooves are formed on only a single surface of thewafer.

A length of solder mass which generally conforms to the shape of onegroove is secured in one of the grooves. In other words, the solderlength is laid within the groove. Because there are a multiplicity ofgrooves, there are also a multiplicity of solder lengths extendingacross the surface of the wafer. A press or die thereafter severs thesolder lengths at each through hole. At this point, the wafer containspin holes having a solder segment located above and below each pin hole.Preferably, the solder segments are disposed between the next adjacentthrough holes.

The pin heads of the first electronic device are thereafter insertedinto the pin holes of the wafer such that the pins emerge on the side ofthe wafer bearing the solder segments. The side of the wafer bearing thesolder segments is then placed against a printed circuit board and thesolder is heated and reflows thus securing the electronic device to theprinted circuit board. The wafer remains disposed between the securelyattached first electronic device and the printed circuit board. Thisfirst application of the present invention involves the use of thepresent solder-bearing wafer with through hole devices, such as thepreviously-described printed circuit board. Through hole devices arethose devices which include a number of holes formed therethrough forreceiving another conductive member, such as conductive pins. It will beappreciated that the wafer may be used with a number of other throughhole devices besides printed circuit boards.

According to another embodiment of the present invention, the firstelectronic device, e.g., a connector, may have the solder holdingfeatures of the wafer incorporated directly into the design of the firstelectronic device. In this instance, a plurality of solder grooves areformed in a surface of the first electronic device so that rows of theconductive pins are disposed between a first groove row and a secondgroove row. It will be appreciated that this surface is preferablyformed of a non conductive material, e.g., a thermoplastic material,which permits the grooves to be easily formed therein. Solder materialis deposited into each solder groove resulting in each pin having onesolder segment on one side thereof and another solder segment on anopposite side thereof. Similar to the first embodiment, the formation ofgrooves serves to limit and define the amount of solder material whichis used for the soldering of one pin to a respective surface of thesecond electronic device. This reduces or eliminates the risk that asingle large mass of solder will result when the solder segments areheated and reflow. In this embodiment, the first electronic deviceincorporates the attributes of the wafer of the first embodiment andtherefore it is not necessary to use the wafer to provide soldermaterial for the soldering of the two devices.

While the first two embodiments of the wafer are intended for use whenthe second electronic device is a through hole type device, anotherembodiment of the wafer of the present invention is intended for use insurface mount type applications. In these applications, planar contactsof the first electronic device are generally disposed flush against aplanar contact surface of the second electronic device to produce anelectrical connection therebetween. For example, the first electronicdevice may comprise a connector referred to as a straddle mount devicein which contacts in the form of fingers seat against respective contactpads formed in the second electronic device. In this embodiment, thewafer also includes solder lengths provided in respective andcomplementary grooves formed in the wafer. The solder lengths aresevered to form distinct solder segments where one or more soldersegments are for the soldering of one contact to one contact pad.

The wafer is disposed against the first electronic device and morespecifically, the wafer extends across the contact fingers thereof suchthat one or more of the solder segments are disposed over one contactfinger. Accordingly, the heating of the solder segments causes thereflowing thereof and because the contacts are preferably formed of asolderable material, the contacts are securely soldered to therespective contact pads providing a secure electrical connection betweenthe first and second electronic devices. Because the wafer includesthrough holes as in the first embodiment, the solder lengths are severedinto the solder segments and therefore a predefined amount of soldermaterial is used in the soldering of one contact to one contact pad.

This embodiment of the wafer of the present invention provides a waferwhich may be used in a variety of surface mount applications. Forexample, not only may the wafer be used to electrically connect astraddle mount device to a printed circuit board, it may also be used inapplications where it is necessary to electrically connect one planarsurface to another planar surface of another electronic device.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects and features of the present invention will be describedhereinafter in detail by way of certain preferred embodiments withreference to the accompanying drawings, in which:

FIG. 1 is a top perspective view of a wafer with pin holes locatedtherethrough;

FIG. 2 is a side perspective view of the wafer of FIG. 1;

FIG. 3 is a top view of the wafer of FIG. 1 additionally havingsolder-holding grooves formed thereon;

FIG. 4 is a top view of the wafer of FIG. 3 additionally having throughholes located therethrough;

FIG. 5 is a cross section view of the wafer of FIG. 4 taken along line5-5;

FIG. 6 is a top view of the wafer of FIG. 5 wherein the solder-holdinglengths have been partitioned;

FIG. 7 is a side view of the wafer of FIG. 6 having the pins of anelectronic device placed through the respective pin holes of the wafer;

FIG. 8 is a bottom plan view of one exemplary electrical connectoraccording to one embodiment of the present invention;

FIG. 9 is a top view of a wafer according to a second embodiment inwhich solder lengths are disposed within solder-holding grooves formedin the wafer;

FIG. 10 is a top plan view of the wafer of FIG. 9 wherein the solderlengths have been partitioned;

FIG. 11 is a side view of an assembly formed of a first electronicdevice coupled to a second electronic device with two wafers of FIG. 10shown exploded therefrom;

FIG. 12 is a side view of the assembly of FIG. 11 with the two wafersbeing applied to a portion of the first electronic device;

FIG. 13 is a side view of the assembly of FIG. 12 showing the firstelectronic device soldered to the second electronic device and the twowafers having been removed from the assembly;

FIG. 14 is a side view of another exemplary wafer according to thepresent invention with solder lengths being provided on both sidesthereof;

FIG. 15 is a side perspective view of a wafer according to anotherembodiment of the present invention;

FIG. 16 is a cross section view taken along the line 16-16 of FIG. 15;

FIG. 17 is a side elevation view of the wafer of FIG. 15 being used toelectrically connect a first electronic device to a second electronicdevice; and

FIG. 18 is a cross section side view of a connector according to anotherembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In one aspect, the present invention facilitates the process ofsoldering electrical terminals or contacts of one electronic device to asurface of a second electronic device using a solder-bearing wafer. Inone exemplary embodiment, the electrical contacts comprise conductivepins and the second electronic device comprises a printed circuit board.FIGS. 1 through 3 illustrate a method of forming a wafer according to afirst embodiment of the present invention.

Turning to FIG. 1, a wafer 100 is provided and is formed of any numberof suitable material and preferably is formed of a non-conductivematerial. For example, the wafer 100 may be formed of a thermoplasticmaterial, thermoset plastic, etc. The wafer 100 has pin holes 110 formedtherethrough. It will be appreciated that pin hole 10 does notnecessarily have to have an annular shape and pin hole 10 generallycomprises small holes formed in the wafer 10. The location and generalspacing of pin holes 110 are determined by the location and spacing ofpins of a first electronic device (FIG. 7) to be mounted onto a secondelectronic device, e.g., a printed circuit board (FIG. 7). It willtherefore be appreciated that the pin holes 110 may be arrangedaccording to any number of patterns depending upon the number of pinholes 110 and the location thereof. In the embodiment shown in FIG. 1,the pin holes 110 are arranged in horizontal rows along a first axis andvertical columns along a second axis and are spaced a predetermineddistance apart from one another. The first axis extends generally acrossa length, L, of the wafer 100 and the second axis extends generallyacross a width, W, of the wafer 100. The first axis is thus preferablylonger than the second axis. The pin holes 110, for example, are spaceda predetermined amount center-to-center along the first axis and apredetermined amount along the second axis to accommodate an electricaldevice having pins that are correspondingly spaced.

Furthermore, the length and width of the wafer 100 generally conform tothe length and width of the first electronic device to be mounted ontothe second electronic device. The depth or thickness of the wafer 100 ispreferably about 0.030 inches. However, this measurement is merely forpurpose of illustration.

The pin holes 110 may be formed through the wafer 100 using any of themethods known in the art, including, e.g., the use of a stamping die.Alternately, the pin holes 110 can be formed or molded duringmanufacture of the wafer 100.

Turning to FIG. 2, therein is illustrated a side perspective view of thewafer 100 where two pairs of the grooves 115 and 117 can be seenextending along the first axis of the wafer 100 on either side of eachrow of the pin holes 110. Although the grooves 115 and 117 are shown ashaving a half-cylindrical shape, it is understood that the shape of thegrooves 115 and 117 may be any shape. Preferably, the shape of thegrooves 115 and 117 conforms to the shape of a solder length 130 (FIG.4) which, as will be described more fully below, is to be inserted ineach of the grooves 115 and 117.

The grooves 115 and 117 are formed in the wafer 100 using any of themethods known in the art, including, e.g., the use of an etching or astamping die. Alternately, the grooves 115 and 117 can be formed duringmanufacture of the wafer 100. For example, the grooves 115 and 117 maybe used during a molding process which is used to manufacture the wafer100. The grooves 115 and 117 may be formed on the wafer 100 before,during or after the placement of the pin holes 110.

Turning to FIG. 3, therein is illustrated the wafer 100 having thethrough holes 120 located therethrough along the first axis so that atleast one through hole 120 is located on either side of each pin hole110. As is shown, each through hole 120 extends sufficiently along thesecond axis to encompass one of grooves 115 and 117, respectively. Thethrough holes 120 are formed on the wafer 100 using any of the methodsdescribed above for forming the pin holes 110 and the grooves 115 and117.

According to the present invention, solder segments 135 are added to thewafer 100 for providing a solder material used to securely attach thefirst and second electronic devices to one another, as will be describedhereinafter. FIGS. 4 through 6 illustrate the method of adding soldersegments 135 to the wafer 100.

Turning to FIGS. 4, and 5 therein is illustrated the wafer 100 havingsolder lengths 130 placed in the grooves 115 and 117. The solder lengths130 include any of the soldering compositions known in the art and arepreferably shaped to be inserted form fittingly and securely within thegrooves 115 and 117. In other words, the solder lengths 130 preferablycomprise elongated strips of solder material which are shapedcomplementary to the grooves 115 and 117. Accordingly, in the presentexample, as particularly illustrated and shown in FIG. 5, the solderlengths 130 are cylindrically shaped so as to fit securely within thehalf-cylindrical shaped grooves 115 and 117 as in FIG. 2.

With continued reference to FIG. 4, it is shown that each pair of solderlengths 130 lie across a row of through holes 120. In this way, a pressor stamp having dies shaped and spaced in conformance with the shape andposition of through holes 120 on wafer 100 is used to sever solderlengths 130 at each of the through holes 120.

FIG. 6 illustrates the wafer 100 after the solder lengths 130 aresevered as described above to form a plurality of solder segments 135.As is shown, each pin hole 110 has one solder segment 135 located oneither side of the pin hole 110. Because each solder segment 135 is heldsecurely by the groove 115 or 117, the wafer 100 can be held in anyposition required to conform to a particular manufacturing process ormachinery being used (e.g., solder side facing-up, facing sideways,facing downward, etc.).

FIG. 7 illustrates an electronic device 150 having pins 140 extendingfrom a first surface 151 thereof. The first electronic device 150 maycomprise any number of suitable devices which are intended to beelectrically connected to a second electronic device 160. For exampleand according to one exemplary embodiment, the first electronic device150 comprises an electrical connector and the second electronic device160 comprises a printed circuit board (through hole type device). Thepins 140 comprise conductive pins which serve to establish an electricalconnection between terminals (not shown) of the first electronic device150 and corresponding electronic components of the second electronicdevice 160. The pins 140 are placed into respective pin holes 110 of thewafer 100. As shown in FIG. 7, the wafer 100 is positioned such that thesolder segments 135 face downwards. Solder segments 135 are held inplace by their form fitting interconnection with grooves 115 and 117.

Once the first electronic device 150 and the pins 140 have been inserteda sufficient distance into the wafer 100 and the pin holes 110, the sideof the wafer 100 having solder segments 135 exposed may be placed ontothe second electronic device 160 having pin holes 110 conforming to thespacing and size of the pin holes 110. The solder segments 135 arethereafter heated causing the solder segments 135 to reflow around thepins 140 and the pin holes 110 along with other surfaces of the secondelectronic device 160. As the solder segments 135 cool, the pins 140 aresecured to the second electronic device 160 resulting in a secureelectrical connection between the first and second electronic devices150, 160. After the reheating and cooling of the solder segments 135,the wafer 100 remains soldered between the first electronic device 150and the second electronic device 160. It being understood that thesolder segments 135 are heated after the first and second electronicdevices 150, 160 have been brought together.

Referring now to FIGS. 1 through 7. It will be appreciated that theprovision of through holes 120 to permit the severing of solder lengths130 also serves to define an amount of solder material around each ofthe pins 140. In other words, by providing two solder segments 135adjacent to each of the pin holes 110, a defined amount of soldermaterial is dedicated for the soldering of one pin 140 to acorresponding section of the second electronic device 160. The severingof the solder lengths 130 reduces the mass of solder material used inthe solder operation which results in a decreased chance that a largesoldered mass will result during the heating process. In addition, thesevering of the solder lengths 130 also prevents adjacent contact sitesfrom being starved. In other words, often the heating of contacts is notuniform and one contact (pin 140) will be heated greater and actuallydraws solder material from one or more adjacent sites. This causes theone or more adjacent contacts to be starved of the solder material andresults in ineffective soldering of these contacts. By placing a definedamount of solder material around each pin 140, the solder material iseffectively divided into local segments which are used for the solderingof one respective pin 140. Accordingly, the heating process producesdistinctly spaced, soldered masses around the pins 140 rather than asingle large soldered mass and the solder starvation sites associatedwith conventional techniques are eliminated.

The solder-bearing wafer 100 of the present invention overcomes many ofthe deficiencies associated with the devices of the prior art. First,the wafer 100 has a relatively simple yet effective design. Because thesolder carrier medium is a thermoplastic material, conductive materialwill not remain attached to the contacts (pins 140) after the soldersegments 135 reflow. Second, thermoplastic materials are typically lesscostly than the metal materials used to produce other soldering aiddevices. Third, this results in reduced manufacturing costs and assimplicity of the present invention permits an operator to more easilyand more quickly apply the wafer 100 to the first electronic device 150.Fourth, the wafer 100 also provides increased solder volumes by formingthe solder segments 135 within the grooves 115 and 117 around therespective pins 140. This increase in solder volume provides more soldermaterial for each solder joint formed between the devices 150, 160,thereby improving the quality of each of the solder joints. Fifth, thepresent invention provides tighter lead spacing in that the contacts(pins 140) of the first electronic device 150 may be closer togetherthan would have been possible if other solder aides were used. Sixth,the solder-bearing wafer 100 permits irregular solder patterns to beformed thereon. This permits the soldering segments 135 to be formed onthe wafer 100 at desired locations. Thus, the location of the soldersegments 135 may be customized depending upon the specific applicationand depending upon the configuration of one or more of the first andsecond electronic devices 150, 160.

Different variations of the solder-bearing wafer 100 are possibledepending on the particular application. For example, only a singlesolder length 130 and single groove may be provided for each row of pinholes. Also, fewer or greater than two rows of pin holes 110 may beprovided on wafer 100. Also, the through holes 120 may not be necessaryif the solder lengths 130 are segmented in a way which allows removal ofthe solder portions in between the desired segments, e.g., by way of acutting and vacuum removal process. Further, the pin holes, throughholes and grooves may take on any necessary shape depending on theparticular application.

It will be appreciated that the wafer 100 may be distributed in a numberof forms. For example, if the specifications of a given application areknown, the wafer 100 may be cut to have a desired length and width sothat the wafer 100 is disposed between the first and second electronicdevices 150, 160 without the wafer 100 extending beyond either of thefirst or second electronic devices 150, 160. The wafer 100 may also berolled onto reels and then distributed to a number ofconnector/electrical component manufacturers for retrofit to theirexisting or future products. The design of the wafer 100 thereforepermits versatility in that it may not only be custom manufactured forone specific application but it also permits the wafer 100 to bedistributed in a basic form and then retrofitted by the purchaser.

Now referring to FIG. 8 in which a first connector device according to asecond embodiment of the present invention is illustrated and generallyindicated at 200. The first connector device 200 is preferably anelectrical connector which is designed to be electrically connected toanother electronic device, such as the printed circuit board 160 shownin FIG. 7. The first connector device 200 is similar to the firstelectronic device 150 of FIG. 7 with the exception that the soldersegments 135 are incorporated as part of the first connector device 200rather than being provided on the wafer 100. In this embodiment, thewafer 100 is not used in the soldering of the first connector device 200to the other electronic device.

As shown in FIG. 8, the first connector device 200 has a first surface202 which faces the second electronic device when the two are solderedto one another. A plurality of pins 210 extend outwardly from the firstconnector device 200 and more specifically, the plurality of pins 210extend away from the first surface 202. The plurality of pins 210 may bedisposed across then first surface 202 according to any number ofpatterns and the row/column pattern shown in FIG. 8 is merely exemplaryin nature. Furthermore, one will appreciate that the pins 140 may haveany number of cross-sectional shapes and the circular cross-sectionshown is also merely exemplary.

According to the second embodiment, grooves 220 are formed across thefirst surface 202 similar to the first embodiment shown in FIGS. 1-7.The grooves 220 are designed to securely carry and locate soldermaterial. In the exemplary embodiment, the grooves 220 extendhorizontally across the first surface 202 with the grooves 220 beingformed on either side of each row of pins 140. Similar to the firstembodiment, the solder material is deposited as defined solder segments135 into the grooves 220 formed in the first surface 202. Each pin 140therefore has a solder segment 135 on one side thereof and anothersolder segment 135 on another side thereof. In one exemplary embodiment,the grooves 220 comprise a number of defined grooves 220 which extendalong a common axis across the first surface 202. Each groove 220therefore has a predetermined length and preferably all of theindividual grooves 220 have the same length. The length of the grooves220 will be determined by a number of factors including the size of thepins 140 and also the amount of the solder material which is to bedeposited around the pin 140. It will be appreciated that in thisembodiment, the grooves 220 are not in the form of single continuousgrooves but rather comprise a number of spaced grooves 220 formed alonga common axis with an ungrooved section 221 formed between adjacentgrooves 220. The grooves 220 may be formed during the manufacture of thefirst connector device 200 or they may be formed by a subsequentoperation, e.g., a stamping operation. Because the pins 140 act asconductive members, the first surface 202 of the first connector device200 is preferably formed of a non-conductive material, such as athermoplastic. This facilitates the formation of the grooves 220 as thegrooves 220 may be formed in the first surface 202 during a moldingprocess, or the like, which is used to form the first connector device200.

After the grooves 220 are formed, the solder material is depositedtherein so that a number of solder segments 135 are provided. Thegrooves 220 may be formed according to any number of known techniques.Each groove 220 defines one solder segment 135. As previously mentionedby forming two opposing grooves 220 around each pin 140, the amount ofsolder material for each pin 140 is generally defined as the amount ofsolder material being deposited within the two opposing grooves 220. Bydividing the solder material into two distinct solder segments 135around each pin 140, the likelihood that a single solid solder mass willresult during reflowing of the solder material is reduced or eliminatedas well as the presence of solder starvation sites is likewiseeliminated. Advantageously, the use of solder segments 135 permits theproper amount of solder material to be delivered to each pin 140 for thesoldering of the pin 140 to the other electronic device, such as aprinted circuit board.

In this embodiment, the wafer 100 of FIG. 1 is not used but rather thesolder holding features are incorporated directly into the design of thefirst connector device 200. This simplifies the soldering operation byeliminating the use of the intermediate wafer 100. Instead, the firstconnector device 200 is directly mated with another electronic device,e.g., a through-hole device, which receives the pins 140 and which arethen soldered to the through hole devices. It will also be appreciatedthat while the first connector device 200 has been described in terms ofcontaining pins 140, the device 200 may contain planar or other shapedcontacts instead of pins 140. The solder segments 135 are simplydisposed around these planar or other shaped contacts for providing asolder and electrical connection between each contact and the secondelectronic device.

FIGS. 9 through 10 illustrate a method of forming a wafer according to asecond embodiment.

Turning to FIG. 9 in which a wafer according to a second embodiment ofthe present invention is illustrated and generally indicated at 300. Thewafer 300 has a length, L, and a width, W. For purpose of illustration,only a section of the wafer 300 is shown in FIGS. 9 and 10. As in thefirst embodiment, the wafer 100 is formed of a non-conductive material,such as a suitable thermoplastic or thermoset material. The wafer 100has a predetermined number of grooves, generally indicated at 310,formed in a first surface 302 of the wafer 300. In the exemplaryembodiment, the grooves 310 comprise longitudinal grooves extendingalong the length L of the wafer 300. The cross-sectional shape of thegrooves 310 may be any shape and in one exemplary embodiment, eachgroove 310 has a half-cylindrical cross-sectional shape. The grooves 310are formed in the wafer 300 using any of the methods known in the art,including, e.g., the use of an etching or a stamping die. Alternatively,the grooves 310 can be formed or molded during the manufacture of thewafer 300.

The wafer 300 also includes a plurality of through holes 320 formed inthe wafer 300. The through holes 320 are formed at spaced locationsalong each groove 310. In other words, through holes 320 are formeddirectly within the groove 310. As shown in FIG. 9, solder lengths 130are placed within each of the grooves 310. Solder lengths 130 arepreferably shaped to be inserted form fittingly and securely within thegrooves 310. In the present example, the solder lengths 130 arecylindrically shaped so as to fit securely within the half-cylindricalshaped grooves 310. Each solder length 130 lies across a row of throughholes 320. In this way, a press or stamp having dies shaped and spacedin conformance with the shape and position of the through holes 320 onthe wafer 300 are used to sever solder lengths 130 at each of thethrough holes 320.

FIG. 10 illustrates the wafer 300 after the solder lengths 130 (FIG. 9)are severed as described above. As is shown, a number of spaced soldersegments 135 are formed. More specifically, one solder segment 135 isformed on either side of one through hole 320. The solder segments 135are still securely fit within the grooves 310 after the performing theoperation to form the solder segments 135. The solder segments 135 arethus axially aligned in rows extending along the length of the wafer 300with one through hole 320 being formed between next adjacent soldersegments 135.

While FIG. 9 shows a pair of grooves 310 and solder lengths 130, it willbe understood that the wafer 100 may contain a single groove 310 andsolder length 130 or the wafer 100 may include more than two grooves 310and solder lengths 130. Furthermore, while the wafer 300 shown in FIG.10, has solder segments 135 formed in a staggered pattern, it will beunderstood that the solder segments 135 may be axially aligned with oneanother in columns as shown in FIG. 11.

The formation of through holes 320 within the wafer 300 and thesubsequent severing of the solder length 130 to form the solder segments135 serve to define the amount of solder material in each of the soldersegments 135. By limiting the solder material to distinct soldersegments 135, the likelihood that a single solid solder mass will resultduring reflowing of the solder material is reduced or eliminated. Incontrast, each of the specific points of contact between the first andsecond electronic devices (not shown) may be provided with a predefinedamount of solder material.

FIG. 11 is a partially exploded side view showing a first electronicdevice 330 and a second electronic device 340. One exemplary firstelectronic device 330 comprises a connector and more particularly, theillustrated first electronic device 330 comprises a connector which iscommonly referred to as a straddle mount device. The device 330 has abase portion 332 and a plurality of contacts 334 extending therefrom.The contacts 334 serve to provide an electrical connection between thefirst electronic device 330 and the second electronic device 340. In theillustrated embodiment, the contacts 334 comprise a number of elongatedfinger-like members which extend outwardly from the base portion 332.Typically, the contacts 334 are formed in opposing rows with a gap beingformed between the rows of contacts 334. The contacts 334 are formed ofa conductive material and preferably, the contacts 334 are formed of asolderable material which aides in the soldering of the first electronicdevice 330 to the second electronic device 340, as will be described ingreater detail hereinafter. This type of contact 334 is also referred toas a solder tail based upon its physical appearance and its materialcharacteristics.

The illustrated first electronic device 330 is referred to as a straddlemount device because the spaced rows of contacts 334 and the baseportion 332 resemble a straddle structure. The first electronic device330 is mounted to the second electronic device 340 by receiving thesecond electronic device 340 within the gap formed between the contacts334. Preferably, the second electronic device 340 comprises a printedcircuit board having a first surface 342 and an opposing second surface344. The second electronic device 340 also has a predetermined number ofsurface mount contact pads 350 formed on each of the first and secondsurfaces 342, 344. These contact pads 350 provide contact surfaces wherean electrical connection is made between the first and second electronicdevices 330, 340 through the contacts 334 and the contacts pads 350. Thecontact pads 350 are therefore spaced along the second electronic device340 in a complementary manner relative to the spacing of the contacts334 so that when the first and second electronic devices 330, 340 matewith one another, the contacts 334 and contact pads 350 engage oneanother.

After the first electronic device 330 has been properly positionedrelative to the second electronic device 340 such that the contacts 334engage the contact pads 350, one or more wafers 300 are brought intocontact with the second electronic device 340 as shown in FIG. 12. FIG.12 illustrates a pair of wafers 300 being disposed against the contacts334 of the first electronic device 330. Generally for each row ofcontacts 334, there will be one complementary wafer 300 used forsoldering the first and second electronic devices 330, 340 to oneanother. More specifically, one wafer 300 is disposed against one row ofcontact 334 and another wafer 300 is disposed against the other row ofcontacts 334. When the wafers 300 are properly disposed against thecontacts 334, the solder segments 135 are brought into contact withthese contacts 334. In other words, one or more solder segments 135seats against an outer surface 335 of one contact 334 and providessolder material for the soldering of the each contact 334 to one contactpad 350. In the illustrated embodiment, two solder segments 135 areprovided for each contact 334. These two solder segments 135 when heatedserve to solder one contact 334 to one contact pad 350. As with theother embodiments, by dividing the solder length 130 into soldersegments 135, the amount of the solder material which is applied for thesoldering of one contact 334 to one contact pad 350 may be controlled.This reduces or eliminates the risk of having a single solder mass formand extend across the surfaces of the first and second electronicdevices 330, 340.

Because the contacts 334 are preferably formed of a solderable material,the heat applied by the solder segments 135 and the reflowing action ofthe solder segments 135 themselves provide an effective solderconnection between the contact 334 and the contact pad 350. This resultsin a secure electrical connection being formed between the firstelectronic device 330 and the second electronic device 340. Dependingupon the specific application, the wafer 300 may or may not be removedfrom the first electronic device 330 during or after the reflowing ofthe solder material. FIG. 13 illustrates the instance where the wafer300 has been removed leaving behind the contacts 334 securely solderedto the respective contact pads 350.

While the embodiment shown in FIGS. 9 through 13 illustrates the wafer300 separate from the first electronic device 330, it is within thescope of the present invention that the first electronic device 330 maybe designed so that the wafer 300 is incorporated therein or coupledthereto prior to attachment to the second electronic device 360. In oneembodiment, the first electronic device 330, e.g., a straddle mountconnector, is directly attached to the second electronic device 340without using a separate wafer 300. Instead the first electronic device330 has the wafer 300 formed as part thereof with each contact 334having one more associated solder segments 135. The first and secondelectronic devices 330, 340 are securely attached to one another bysimply inserting the second electronic device 340 between the contacts334 so that the contacts 334 seat against the conductive pads 350 of thesecond electronic device 340. Heating action on the solder segments 135causes reflowing of the solder material resulting in the contacts 334being securely attached to the contact pads 350.

It will be appreciated that instead of being integrally formed with thefirst electronic device 330 (or first electronic device 150), the wafer300 (or wafer 100) may be attached to the respective first electronicdevice by any number of techniques. For example, the wafer may havelocking features which cooperate with complementary locking featuresprovided on the first electronic device so as to securely attach thewafer to the first electronic device. The first electronic device may bemarketed and distributed this way, namely with the wafer being attachedand preferably detachably attached to the first electronic device toform an assembly. The assembly is then coupled to the respective secondelectronic device 160, 340 and then heated to cause the solder materialto reflow and electrically connect the respective components.

The embodiment illustrated in FIGS. 9 and 10 provides an attractivealternative to using a ball grid array type device for surface mountlead type devices. As is known, ball grid array type devices generallycomprise connector devices which have surface mountable ball gridarrays. The ball grid array is in the form of a plurality of solderballs arranged across an outer surface of the connector according to anynumber of patterns. One typical arrangement is for the solder balls tobe arranged in a number of rows and columns. Upon heating, the solderballs reflow and create a soldering surface for securely attaching theconnector device to another device such as a planar pad of a printedcircuit board.

Wafer 300 offers several advantages over using a ball grid array typeconnector. First, the formation of the plurality of distinctly arrangedsolder balls is not a simple task and requires a significant amount oftime and skill. Thus, ball grid array type connectors are usually costlybecause of the time and skill required to manufacture such connectors.In contrast, the wafer 300 of the present invention offers improvedreliability with significantly lower manufacturing and raw materialcosts.

FIG. 14 illustrates yet another wafer 400 for use in soldering oneelectronic device to another electronic device. The wafer 400 is similarto the device 300 with the one difference being that the solder materialis applied to both sides of the wafer 400. Thus, grooves 310 are formedon both sides of the wafer 400 so that solder segments 135 may be formedon both sides. This type of wafer 400 may be used to solder planar padsof one electronic device, such as a printed circuit board, or a ceramicwafer (not shown) to planar pads of another electronic device or otherceramic wafer (not shown). It is intended that the wafer 400 may be usedin any type of connector environment where a surface mount connector isparticularly suited for use.

Turning now to FIGS. 15 through 17 in which yet another wafer accordingto another embodiment is shown and generally indicated at 500. As withthe wafers of the other embodiments, the wafer 500 is preferably formedof a non-conductive material, such as a thermoset plastic orthermoplastic. In this embodiment, the wafer 500 is intended to be usedin ball grid array type applications where a first generally planarelectronic device 510 is electrically connected to a second generallyplanar electronic device 520. In one embodiment, the first generallyplanar electronic device 510 has at least one first contact 512 and thesecond electronic device 520 has at least one second contact 522. Thefirst contact 512 may be in the form of a planar contact pad or the likeor may be a solder ball in the case of a ball grid array type package.Similarly, the at least one second contact 522 may be in the form of aplanar contact pad or the like or may be a solder ball. As is known,solder ball grid array type devices have a plurality of solder ballsformed on a planar surface where each solder ball is associated with onecontact terminal. The solder ball is then heated after the twoelectronic devices are positioned relative to one another to causereflowing of the solder material to provide an electrical connectionbetween the two contacts 512, 522.

FIG. 15 shows the wafer 500 in partial view. The wafer 500 generallyincludes a first end 502 and an opposing second end (not shown) alongwith a first side 504 and an opposing second side 506. The wafer 500 hasone or more solder segments 530 disposed within the wafer 500 accordingto a predetermined pattern. Generally, there will be at least one soldersegment 530 for each pair of electrical contacts 512, 522. In otherwords, one or more solder segments 530 are used to solder the one of thefirst contacts 512 to one of the second contacts 522 and provide anelectrical connection therebetween. In the exemplary embodiment shown inFIG. 15, each solder segment 530 is fitted into a solder opening 540formed in the wafer 500. The solder opening 540 extends completelythrough the wafer 500 so that the solder segment 530 preferably extendsbeyond both a first surface 501 and a second surface 503, as best shownin FIG. 16. This permits one solder segment 530 to be used to provide asolder connection between the first surface 501 and the first electronicdevice 510 and the second surface 503 and the second electronic device520.

The wafer 500 also has a plurality of through holes 550 formed therein.The through holes 550 are arranged and formed in the wafer 500 such thatone through hole 550 intersects one end of the solder opening 540 andanother through hole 550 is formed at the opposite end of the solderopening 540 in an intersecting manner. Accordingly, the solder opening540 opens into one through hole 550 at one end and the opposing throughhole 550 at the other end. In one exemplary embodiment, each throughhole 550 has a first axis extending along a length thereof and eachsolder opening 540 has a second axis extending along a length thereof.In the illustrated embodiment, the first and second axes aresubstantially perpendicular to one another. Each first axis issubstantially parallel to the first end 502 and substantiallyperpendicular to the first and second sides 504, 506, respectively. Eachsecond axis is therefore substantially parallel to the first and secondsides 504, 506 and substantially perpendicular to the first end 502.

Because the solder opening 540 extends between two spaced through holes550, opposing platforms 560 are formed and partially defined by thesolder opening 540 and the through holes 550. FIG. 16 is a cross sectionview taken along a line 16-16 of FIG. 15 which cuts through theplatforms 560. Thus, it will be appreciated that the edges of theplatforms 560 serve to retain and hold the solder segment 530therebetween within the solder opening 540. This design permits a singlesolder segment 530 to be used to provide a solder connection at opposingsurfaces 501, 503 of the wafer 500. It will be appreciated that thenumber of solder segments 530 used and therefore the number of solderopenings 540 and through holes 550 which are formed in the wafer 500will typically depend upon the given application. More specifically andaccording to one embodiment, one solder segment 530 is used to provideboth a solder and electrical connection between one first contact 512and one second contact 522. Thus, if there are a multitude of first andsecond contacts 512, 522 provided on the respective first and secondelectronic devices 510, 520, there were will be a corresponding numberof solder segments 530.

FIG. 17 illustrates the use of the wafer 500 in electrically connectingthe first and second electronic devices 510, 520. Preferably, thedimensions of the wafer 500 are such that the wafer 500 is convenientlydisposed between the first and second electronic devices 510, 520without extending therebeyond. After disposing the wafer 500 between thefirst and second devices and aligning the first and second contacts 512,522 relative to one another and then aligning each solder segment 530relative to the first and second contacts 512, 522 such that the eachsolder segment 530 is in contact with or proximate to both of the firstand second contacts 512, 522, the solder segments 530 are heated byknown techniques. The heating of the solder material causes the soldermaterial to reflow over both the first and second contacts 512, 522.Because the solder material comprises a conductive material, anelectrical connection is provided from the first electrical device 510to the second electrical device 520 through the first and secondcontacts 512, 522.

As with the other embodiments, the formation of the through holes 550serves to define distinct segments of solder material which are used inthe solder and electrical connection of one first contact 512 to onesecond contact 522. As previously-mentioned, this advantageouslyprevents a single mass of solder material from being formed during thesolder operation and also prevents solder starvation sites from formingwithin the wafer 500.

The wafer 500 thus provides an attractive method of electricallyconnecting a first planar device (e.g., device 510) to a second planardevice (e.g., device 520) where the wafer 500 is designed to besandwiched between these devices 510, 520 yet at the same time provideelectrical connections between corresponding electrical contacts. Notonly does wafer 500 find particular utility in ball grid array typeapplications but also in applications where one planar printed circuitboard is electrically connected to another printed circuit board. Itwill be appreciated that the shapes and sizes of the solder segments530, the solder opening 540, and the through holes 550 may varyaccording to the given application and are not critical to the practiceof the present invention. Broadly, the wafer 500 comprises a member inwhich a single solder segment disposed therein serves to electricallyconnect the first device 510 disposed against the first surface 501 ofthe wafer to the second device 520 disposed against the second surface503.

Turning now to FIG. 18 in which yet another embodiment of the presentinvention is illustrated. In the embodiment of FIG. 18, thesolder-bearing features of the wafer 500 are incorporated into the firstelectronic device 510. A solder-bearing member 511 forms a part of thefirst electronic device 510 such that one or more solder segments 530are aligned with one first contact 512 of the first electronic device510. Similar to the wafer 500, the solder segments 530 are disposedwithin solder openings 540 and extend completely through thesolder-bearing member 511 so as to be accessible to both opposingsurfaces of the solder-bearing member 511. It will be appreciated thatthe solder-bearing member 511 may be a separate member such as the wafer500 which is securely attached to the first electronic device 510 or thesolder-bearing member 511 may be integrally formed with the firstelectronic device 510. In both instances, the solder-bearing member 511is preferably formed of a non-conductive material, such as athermoplastic or thermoset plastic.

In this embodiment, the one or more solder segments 530 provide anelectrical pathway to one first contact 512. Each solder segment 530includes a first portion 517 which is disposed in intimate contact withor proximate to the first contact 512 and a second portion 519 which isformed on the opposite side of the solder-bearing member 511. The secondportion 519 is thus designed for positioning relative to the secondcontact 522 to form an electrical and solder connection therewith uponheating. By depositing one or more solder segments 530 over each firstcontact 512, the first electronic device 510 may be easily electricallyconnected to the second electronic device 520 by positioning the firstelectronic device 510 relative to the second electronic device 520 suchthat the second portions 519 are aligned with the second contacts 522.The second portions 519 may be in intimate contact with or proximate tothe second contacts 522 when the first and second electronic devices510, 520 are positioned and coupled to one another. Upon heating, thesolder segments 530 reflow and provide the desired electrical connectionbetween the first and second contacts 512, 522. More specifically, thefirst portion 517 reflows over the first contact 512 and the secondportion 519 reflows over the second contact 522.

Various embodiments of the present invention thus provides a waferdesigned to carry solder material, whereupon heating and placement ofthe wafer relative to the first and second electronic devices, thesolder material acts to securely attach a first contact of the firstelectronic device to a second contact of the second electronic device.Advantageously, the wafer may be used in a variety of settings includingthrough hole electronic devices and also surface mount applications. Thewafer has a simple yet effective design with increased applicationpotential relative to conventional connecting devices.

Although a preferred embodiment has been disclosed for illustrativepurposes, those skilled in the art will appreciate that many additions,modifications and substitutions are possible without departing from thescope and spirit of the invention.

1. An electrical connector to be electrically connected to a secondelectronic device having at least one second contact comprising: asubstrate having a first surface and at least one first contactextending outwardly from and integrally connected to the first surface,wherein the first surface includes a surface feature formed as a partthereof proximate the at least one contact; and a mass of soldermaterial retainingly held on the surface feature of the first surfacewhich is for placement against the second electronic device such thatthe first and second contacts are aligned and whereupon heating of themass of solder material, the first and second contacts are securelyattached to one another and form an electrical connection therebetween,wherein the first contact extends outwardly from the first surfacebeyond the mass of solder material.
 2. The electrical connector of claim1, wherein for each contact, there are a pair of features with a pair ofmasses of solder material retained thereon, the pair of features beingon opposite sides of the at least one contact.
 3. The electricalconnector of claim 1, wherein the first contact comprises a pin contact.4. The electrical connector of claim 1, wherein the feature comprises agroove formed in the first surface, the groove having a floor on whichthe mass of solder material sits.
 5. The electrical connector of claim1, wherein the feature comprise a first row of axially arranged featuresand a second row of axially arranged features with the first contactsbeing axially arranged between the first and second rows.
 6. Theelectrical connector of claim 1, wherein the mass of solder materialcomprises a solder segment.
 7. The electrical connector of claim 1,wherein the second contact comprises a printed circuit board associatedwith the second electronic device.
 8. The electrical connector of claim1, wherein the surface feature comprises an alteration to the firstsurface.
 9. The electrical connector of claim 1, wherein the surfacefeature is located relative to the first contact such that heating ofthe mass of solder material causes the solder material to reflow aroundthe first contact.
 10. An electrical connector to be electricallyconnected to a second electronic device having at least one secondcontact comprising: a substrate having a first surface and a row offirst contacts extending outwardly from and integrally a part of thefirst surface, wherein the first surface includes axial arrangements offeatures formed as a part thereof proximate the rows of first contacts,where each row of first contacts is disposed between a pair of axiallyarranged features, the first contacts being axially aligned; and aplurality of solder masses retainingly held on the surface features ofthe first surface which is for placement against the second electronicdevice such that first and second contacts are aligned and whereuponheating of the mass of solder material, the first and second contactsattached to one another and form an electrical connection therebetween,wherein the first contacts extend beyond the solder masses.
 11. Theelectrical connector of claim 10, wherein the features include a firstrow of axially arranged features and a second row of axially arrangedfeatures with one row of first contacts being axially arranged betweenthe first and second rows.
 12. The electrical connector of claim 10,wherein the surface feature is located relative to the first contactsuch that heating of the mass of solder material causes the soldermaterial to reflow around the first contact.
 13. An electrical connectorto be electrically connected to a second electronic device having atleast one second contact comprising: a single substrate having a firstsurface and a thickness, the single substrate having at least one firstcontact extending outwardly from the first surface, wherein the firstsurface includes a surface feature formed as a part thereof proximatethe at least one contact and the surface feature has a floor on which amass of solder material rests; and the mass of solder materialretainingly held on the surface feature of the first surface which isfor placement against the second electronic device such that the firstand second contacts are aligned and whereupon heating of the mass ofsolder material, the first and second contacts are securely attached toone another and form an electrical connection therebetween, wherein adepth of the surface feature is less than the thickness of the substrateso that the surface feature is completely contained in the singlesubstrate.